This invention relates to vehicles having front mounted engines and in particular to such vehicles as are provided with means for restraining the forward motion of the engine in the event the engine is severed from the chassis on the occurrence of a frontal collision.
When a vehicle equipped with a front mounted engine is involved in a frontal accident above a predetermined vehicle speed, the mountings of the engine and transmission unit are often released from the chassis of the vehicle. These mounting units are generally comparatively soft to prevent the transmission of engine vibrations from the engine and transmission unit to the chassis of the vehicle during normal engine operation. On the release of these mountings from the chassis, the engine unit with the transmission moves at a substantially undiminished velocity toward the front of the vehicle.
It has previously been considered that the release of the engine and transmission unit from the chassis of the vehicle was unobjectionable or even desirable. It was previously felt that this spearation resulted in protection of the passenger compartment and therefore the vehicle occupants in the compartment against dangerous deceleration, since a large amount of kinetic energy remained with the engine/transmission unit which was projected forward.
Investigations have disclosed that in the event of a frontal accident, when the engine and transmission of the vehicle are projected forward from the chassis into a relatively unmovable object, such as a stone wall or a heavier vehicle, the engine and transmission following destruction of their suspension will hit the relatively rigid front structure of the object or stronger vehicle, and will be pushed back by it and crash into the passenger compartment of the vehicle at a comparatively high speed. This reflection-like process stresses a weaker vehicle involved in a head-on collision, with simultaneous relief to a stronger vehicle, considerably more than would be the case if the vehicle had crashed at half of the collision speed into a rigid object. In addition, a weaker vehicle involved in a head-on collision is subjected to a considerable additional stress in that it is hit by the engine of the stronger vehicle and must intercept it.
It has consequently been determined that it is advisable to restrain this forward motion of the vehicle engine/transmission unit following release from the chassis of the vehicle. It is also desirable to deflect the forward motion of the engine toward the ground in order that its kinetic energy be dissipated in a direction which is not harmful to the passenger compartment of the vehicle and will not pose a hazard to its occupants.
There have been known in the prior art such structural designs for restraining the forward motion of a vehicle engine. German patent disclosure No. 2,241,651 discloses an engine mounting arrangement in which the engine and transmission unit is mounted by releasable mounts at the rear portion and is also affixed to a pivotable transverse structural member at the front end of the chassis. When a vehicle with such a mounting arrangement is involved in a frontal collision the engine and transmission unit is released from its rear mount and swivels about the forward transverse structural member in a downward direction toward the road. Accordingly, the penetration of the engine and transmission unit into the passenger compartment as the result of the collision is avoided. Such an arrangement requires that the transverse structural member have sufficient structural strength and rigidity to counteract the forward inertia of the engine and cause a swiveling effect resulting in a downward motion of the engine and transmission.
The problem with this prior art engine mounting arrangement is that the pivotable connections between the engine and the transverse supportant member at the front end of the engine constitute a vibration transmitting connection between the point of the engine/transmission unit having maximum amplitude of vibration and the automobile chassis. Consequently, engine vibrations are transmitted to the chassis with a high amplitude during normal operating conditions.
It is therefore an object of the present invention to provide a vehicle with a restraining means for a front engine in the event of a frontal collision, which means do not impair driving comfort by transmitting engine vibrations to the chassis.